1. Field of the Invention
The present invention relates to a structure of a cartridge for accommodating an information-recording medium including a substrate made of resin or plastic. In particular, the present invention relates to a cartridge which makes it possible to avoid deformation during storage of an information-recording medium such as an optical recording medium and a magnetic recording medium accommodated in the cartridge.
2. Description of Related Art
Recently, a variety of high density information-recording media are commercially available, which are represented by compact disks (CD), magneto-optical recording media (MO), optical recording media such as digital versatile disks (DVD), and magnetic recording media such as hard disks. Usually, a substrate made of plastic such as polycarbonate is used for the optical recording media. Even in the case of the hard disk, it is known to use a plastic substrate formed with emboss type pre-pits. Since the injection molding is available to produce the plastic substrate, the plastic substrate is suitable for mass-production. However, in view of the properties of the plastic substrate, the plastic substrate involves a problem that deformation such as warpage and flexure tends to occur as compared with substrates made of aluminum or glass.
A permissible standard value is specified for the optical disk in relation to the deformation such as warpage. For example, in the case of a rotary type recording disk of 5.25 inches (133 mm), the permissible standard value for the amount of disk deformation is determined as a tilt in a direction toward the outer circumferential end from the center of rotation of the disk, which is not more than xc2x1(diameter of disk recording medium)xc3x97sin((0.5 to 0.6)xc3x972xcfx80/360), i.e., not more than about 0.58 to 0.70 mm.
If the deformation of not less than about 0.58 to 0.70 mm occurs, for example, in the optical disk or the magneto-optical disk of 5.25 inches (133 mm), the following trouble is caused. For example, when a magneto-optical disk having a diameter of 5.25 inches and a thickness of 0.6 mm is accommodated in a cartridge, a space of a slight width of 1.5 to 1.7 mm exists between the surface of the magneto-optical disk and the inner wall of the cartridge. Therefore, when the disk having the radius of 67 mm is rotated, if the value of surface deflection caused by deformation of the disk becomes not less than 1.5 to 1.7 mm concerning one side (not less than 3.6 to 4.0 mm concerning both sides) in a direction perpendicular to the disk surface, then the disk collides with the cartridge, and the disk is possibly destroyed. It is also feared that the surface deflection may cause collision between the disk and the optical head or the magnetic head of the recording and reproducing apparatus during rotation of the disk, resulting in breakage of the disk or the head. Therefore, the deformation of the substrate relates to an extremely serious problem concerning the information-recording medium on which recording or reproduction is performed while accommodating the information-recording medium in a case or a cartridge.
For example, FIG. 25A shows a state in which a cartridge case 73 is allowed to stand perpendicularly, wherein a disk 1 produced with a plastic substrate is accommodated in the cartridge case 73. In order to successfully rotate the disk 1 in the cartridge for the purpose of recording or reproduction, a gap is provided between the inner wall of the cartridge case 73 and the surface of the disk 1. Therefore, as shown in FIG. 25A, the disk 1 leans obliquely against the inner wall in the cartridge case 73 which stands perpendicularly. In such an arrangement, for example, if the disk 1 is left for a long period of time in a situation in which the maximum temperature is not less than 40xc2x0 C. and the maximum humidity arrives at 90% RH, the warpage 14 occurs in the vicinity of the outer circumference of the disk 1 as shown in FIG. 25B.
As shown in FIG. 26A, if the cartridge case 73 is left to lean against the wall under a similar environmental condition, the warpage 14 occurs in the vicinity of the outer circumference of the disk 1 as shown in FIG. 26B.
As shown in FIGS. 27A and 27B, it is assumed that a disk recording medium 1 is placed and stored in a cartridge 73 which has a stud 13 only at its inner circumferential portion. When the disk is thin, and the diameter of the stud 13 is small as compared with the diameter of the disk, then the warpage 14 has sometimes occurred at the outer circumference of the disk 1 as shown in FIG. 27B. When such a cartridge 73 is left to lean obliquely against a perpendicular wall, if the environmental temperature and the environmental humidity are severe as described above, the deformation 14 of the disk 1 has occasionally occurred as shown in FIG. 28.
Even in the case of a conventional disk produced by using a substrate made of resin such as polycarbonate and polymethyl methacrylate, when the disk has a large diameter, it is possible to counteract the deformation such as warpage by using a thick resin substrate. In the market, for example, the following characteristics are demanded for the medium at present and in future: i) the information-recording density is extremely high, ii) the dimension such as diameter and thickness is smaller, iii) the medium has a light weight and it is hardly broken, and iv) the medium is usable at high speed rotation. In order to satisfy the foregoing demands, for example, it is necessary for the magneto-optical disk that the thickness of the plastic substrate such as polycarbonate and polymethyl methacrylate is not more than 0.8 mm, especially not more than 0.6 mm. However, if the thickness of the plastic substrate is made thin as described above, the problem of deformation such as warpage becomes conspicuous.
In general, the warpage of the disk occurs when the medium is stored or used in an environment which is different from the environment of temperature and humidity during the production of the recording medium. It has been revealed that the larger the difference in environment is, the more conspicuous the warpage is. The magnitude of warpage differs depending on the difference in type of the plastic material of the substrate. It has been also revealed that the magnitude of warpage differs depending on the type and the thickness of the material for a protective film for coating the substrate.
A first object of the present invention is to provide a novel cartridge for accommodating an information-recording medium based on the use of a plastic substrate, which makes it possible to avoid any deformation such as warpage and flexure of the recording medium in the cartridge during storage even when the cartridge is stored in any posture.
A second object of the present invention is to provide a novel cartridge which makes it possible to avoid any deformation such as warpage and flexure of a recording medium as accommodated obliquely therein even when the cartridge is left to stand perpendicularly or even when the cartridge is left to lean against a wall.
A third object of the present invention is to provide a novel cartridge for accommodating an information-recording medium based on the use of a plastic substrate, in which the cartridge is prevented from such an arrangement that the cartridge stands perpendicularly or the cartridge leans against a wall.
According to a first aspect of the present invention, there is provided a cartridge for accommodating an information-recording medium, comprising:
a cartridge case on which a window for accessing the information-recording medium in the cartridge is formed;
a shutter used for opening and closing the window; and
a deformable elastic member provided on an inner surface of the shutter, for making contact with the information-recording medium accommodated in the cartridge case so that the information-recording medium is fixed in the cartridge case when the shutter is closed, wherein at least a part of the deformable elastic member is retracted into a space between the inner surface of the shutter and a surface of the cartridge case when the shutter is open.
The cartridge of the present invention functions such that when the shutter is closed, the information-recording medium such as a magneto-optical disk is pressed in the cartridge case by means of the elastic member provided on the inner surface of the shutter. Accordingly, for example, even when the user arranges the cartridge in a state in which the cartridge stands perpendicularly as shown in FIG. 25A or in a state in which the cartridge leans against the wall surface as shown in FIG. 26A, the information-recording medium is fixed by the elastic member in the cartridge as shown in FIG. 1C. Therefore, the information-recording medium is prevented from movement in the cartridge, which would otherwise result in a posture liable to cause deformation such as warpage and flexure. Even when the cartridge is vibrated, it is impossible for the information-recording medium to move in the cartridge. Therefore, any damage of the information-recording medium is avoided, which would be otherwise caused by collision of the information-recording medium with the inner wall of the cartridge.
Especially, the elastic member urges the information-recording medium accommodated in the cartridge case so that the information-recording medium is pressed against the inner wall of the cartridge case. Therefore, no partial load is exerted on the outer circumferential portion of the information-recording medium. Even when the cartridge is left to stand perpendicularly or obliquely for a long period of time, the deformation does not occur in the information-recording medium, which would be otherwise caused by warpage and flexure.
When the shutter is open, at least the part of the elastic member is retracted into the space between the inner surface of the shutter and the surface of the cartridge case. Therefore, the elastic member does not inhibit the rotational motion of the information-recording medium as well as the recording or reproducing operation accompanied thereto. The elastic member may have a shape of plate or wire. When a plate spring is used as the elastic member, the entire plate spring may be retracted into the space between the inner surface of the shutter and the surface of the cartridge case when the shutter is open. Accordingly, it is possible to produce the compact cartridge while giving the effect of the present invention which is provided when the shutter is closed as described above. The cartridge of the present invention has exactly the same appearance as those of conventional cartridges, while avoiding the warpage and flexure of the information-recording medium.
The window may include a pair of window openings which are formed through both surfaces of the cartridge case so that the information-recording medium is accessible from both sides of the cartridge case. The shutter may include a pair of shutter planes used for opening and closing the pair of window openings. The elastic member may be provided on each of inner surfaces of the shutter planes so that the information-recording medium may be interposed and fixed between the elastic members in the cartridge case.
The elastic member may be a wire spring. One end of the wire spring may be secured to the inside of the cartridge case, and the other end may be secured to the inner surface of the shutter. The wire spring is bent so that its bent section urges the information-recording medium against an inner wall of the cartridge case when the shutter is closed, and a part of the wire spring is retracted into the space between the inner surface of the shutter and the surface of the cartridge case when the shutter is open.
According to a second aspect of the present invention, there is provided a cartridge for accommodating an information-recording medium, comprising:
a cartridge case on which a window for accessing the information-recording medium in the cartridge is formed;
a shutter used for opening and closing the window, the shutter having a projection provided on its inner surface; and
a pressing member supported in the cartridge case to be capable of elastic deformation, for being urged by the projection to press the information-recording medium so that the information-recording medium is fixed in the cartridge case when the shutter is closed, wherein the pressing member is disengaged from the information-recording medium when the shutter is open.
According to the cartridge concerning this aspect, the projection, which is provided on the inner surface of the shutter, urges the pressing member when the shutter is closed. The urged pressing member is moved toward the information-recording medium, and it contacts with the information-recording medium so that it presses the information-recording medium. As a result, the information-recording medium is pressed against the inner wall of the cartridge case, and it is fixed in the cartridge (see FIG. 9B). Accordingly, no partial load is exerted on the outer circumferential portion of the information-recording medium. Even when the cartridge is arranged perpendicularly or obliquely for a long period of time, no deformation occurs, which would be otherwise caused by warpage or flexure in the information-recording medium. The damage to the information-recording medium is avoided, which would be otherwise caused by collision of the information-recording medium with the inner wall of the cartridge as described above.
A groove, into which the projection is inserted to slide therein when the shutter is opened, may be formed on the cartridge case. As shown in FIGS. 7A to 7C, a part of the cartridge case may be used to form the pressing member. An area for forming the pressing member may be defined by cutting out a predetermined area (central area 65) of the cartridge case. The pressing member may be defined, for example, by cutting out an area of the cartridge case so that a spindle hole is surrounded thereby. In this embodiment, the pressing member is integrated with the cartridge case. Therefore, it is unnecessary to separately provide any additional member. Thus, the cartridge can be designed in a simple and compact form.
Alternatively, the pressing member may comprise a pressing section for pressing the information-recording medium, and an arm for movably supporting the pressing section in the cartridge case. In a specified embodiment, the pressing section may be supported between a pair of arms, and the pressing section may have a pressing surface for pressing the information-recording medium and a contact surface disposed on a side opposite to the pressing surface, for making contact with the projection (see FIGS. 9A and 9B). When the arm is composed of a plate spring, the amount of movement of the pressing section, which is provided when the shutter is opened and closed, can be adjusted in accordance with the length of the arm. In another specified embodiment, the cartridge may be constructed such that one end of the arm is secured to an inner wall of the cartridge case, the other end of the arm is coupled to the pressing section, a part of the arm is bent to form a protrusion which is convex toward the outside of the cartridge case, and the protrusion is urged by the projection when the shutter is closed (see FIG. 9B).
According to a third aspect of the present invention, there is provided a cartridge for accommodating a planar information-recording medium movably in the cartridge, wherein:
a sliding material is applied to at least a part of an inner wall surface (inner circumferential side wall) of the cartridge opposing to an outer circumference of the information-recording medium in the cartridge, and thereby the outer circumference of the information-recording medium slides easier on the sliding material than on a material for constructing the inner wall surface of the cartridge.
According to the cartridge concerning the third aspect of the present invention, the sliding material is applied to the inner circumferential side wall. Therefore, as shown in FIG. 23A, even when the cartridge is allowed to lean against the wall, the information-recording medium can be moved with its outer circumference sliding on the inner circumferential side wall. As a result, the information-recording medium is positioned in the cartridge so that the whole of one planar surface of the information-recording medium contacts with one inner wall surface of the cartridge opposing to the planar surface of the information-recording medium. Therefore, the information-recording medium is prevented from being arranged in a posture which tends to cause deformation such as warpage and flexure in the cartridge. Those usable as the sliding material include, for example, titanium nitride, silicon nitride, aluminum nitride, silicon carbide, and silicon oxide.
According to a fourth aspect of the present invention, there is provided a cartridge for accommodating a planar information-recording medium movably in a cartridge case, wherein:
a pair of long sides, which define at least one side surface of the cartridge case, are processed to form a curved surface having a curvature of not less than 2 mm (2 mmxe2x89xa6r).
According to a fifth aspect of the present invention, there is provided a cartridge for accommodating a planar information-recording medium movably in a cartridge case, wherein:
at least one side surface is processed to form a curved surface having a curvature of not less than 2 mm.
In the cartridges according to the fourth and fifth aspects of the present invention, the side surface or the portions of the pair of long sides (ridges) for defining the side surface forms the curves surface with the curvature described above. Therefore, it is difficult for the user to leave the cartridge standing perpendicularly or obliquely. It is possible to avoid the posture which causes warpage and flexure of the information-recording medium in the cartridge. The portion, which is processed to have the curvature r, may be coated with a material which causes smooth sliding movement as compared with a material for constructing the cartridge. When the cartridge is formed with a window, and it further comprises a shutter used for opening and closing the window, then a corresponding portion of the shutter, which covers the side surface processed to have the curvature r, may be also processed to have the curvature r.
According to a sixth aspect of the present invention, there is provided a cartridge for accommodating a planar information-recording medium movably in a cartridge case, wherein:
at least a side surface of the cartridge case and a portion in the vicinity thereof are coated with a material which causes smooth sliding movement as compared with a material for constructing the cartridge, and a pair of long side portions of the side surface form a curved surface.
In the cartridge according to the sixth embodiment of the present invention, the side surface of the cartridge case and the portion in the vicinity thereof are coated with the material which causes smooth sliding movement as compared with the material for constructing the cartridge. Therefore, even when it is intended that the side surface of the cartridge case is allowed to contact with the floor or ground to stand the cartridge perpendicularly or obliquely, the cartridge easily slides and falls down to take a horizontal arrangement. Accordingly, the information-recording medium is prevented from being arranged in a posture which causes warpage and flexure in the cartridge. Those used as the material which causes smooth sliding movement include, for example, ceramics such as titanium nitride, metals such as nickel, and resins such as polyacetal and polytetrafluoroethylene.
The cartridge of the present invention may contain the information-recording medium in the cartridge case. The information-recording medium may be an arbitrary recording medium with its substrate made of a plastic material, including, for example, magneto-optical disks, phase-change optical disks, DVD, and removable hard disks.